(1) Field of the Invention
The present application relates to flow control in high speed cell switching networks. More particularly, the invention relates to a method and system for reserving bandwidth for very bursty ATM connections according to (1) traffic parameters and tolerance values declared at call setup and (2) policing the traffic according to the Generic Cell Rate Algorithm (GCRA) associated with the bandwidth reservation.
(2) Background Information
Asynchronous Transfer Mode (ATM)
The "Broadband Integrated Services Digital Network" or B-ISDN is a new telecommunication technology developed by the telecommunications (carrier) industry for both the data transmissions (computer) and the telecommunications (telephone). This is conceived as a carrier service to provide high speed communications to end users in an integrated way. The technology selected to deliver the B-ISDN service is called "Asynchronous Transfer Mode" or ATM. The almost universal acceptance of ATM comes from the fact, that:
ATM handles all the different kinds of communication traffic, as voice, data, image, video, high quality sound, multimedia and many others, PA1 ATM can be used in both the LAN (Local Area Network) and the WAN (Wide Area Network) network environments and hence promises a seamless interworking between the two. PA1 TRANSIT NODES: They perform the backbone data transport within the ATM network. Transit Nodes connected to a different ATM network must implement the Network Node Interface (NNI). PA1 ACCESS NODES: They are Network Nodes located at the boundary of an ATM network where ATM end points are connected. Access Nodes implement the User Network Interface (UNI). PA1 Those that interface to the ATM network directly through either the public UNI or a private UNI. PA1 Those that do not know anything about ATM and interface using a non-ATM protocol (such as Frame Relay, TCP/IP). PA1 For real-time traffic such as voice or video, cells can be lost but a delay in transmission is unacceptable. Real-time traffic has very stringent delay and jitter requirements. PA1 When non real-time traffic (such as data) is transferred, a delay is acceptable but the cells cannot be lost. PA1 Cell Loss Ratio (CLR) (the CLR expresses the likelihood that a cell will not reach its destination or not reach it by the time promised), PA1 End-to-end Cell Transfer Delay (CTD), PA1 End-to-end Cell Delay Variation (CDV, also called delay jitter), PA1 . . PA1 At connection admission time, and PA1 Once the connection is established. PA1 determining a Cell Delay Variation Tolerance bound value (CDVT sub bound), PA1 reserving bandwidth in order to satisfy the specified quality of service if the declared Cell Delay Variation Tolerance (CDVT) value is less than or equal to the Cell Delay Variation Tolerance bound value (CDVT.sub.bound) PA1 reserving bandwidth and policing traffic in order to satisfy a quality of service based on new defined traffic parameters and tolerance values, if the declared Cell Delay Variation Tolerance (CDVT) value is greater than the Cell Delay Variation Tolerance bound value (CDVT.sub.bound)
Thus ATM is effective in a much wider range of communications environments than any previous technology. It provides high bandwidth, low delay, fixed length cell based transfer mode technique (an ATM cell has a length of 53 bytes, 48 bytes for payload and 5 bytes as header), and allows multiplexing and switching of different types of traffic in an integrated way, while optimizing the network resources utilization.
The conceptual structure of an ATM network is shown in FIG. 1.
ATM Networks
FIG. 1 shows a typical ATM network composed by three quite separate networks--two private 101a and 101b and one public 102. Private ATM networks are sometimes called "Customer Premises Networks" and indeed they will very often be confined to a local area such as a building or a campus. However, a private ATM network can be distributed over a wide area by the use of non-ATM links between nodes. Such links could be copper-wire leased lines, "dark" fibers or Sonet/SDH TDM (Synchronous Optical Network/Synchronous Digital Hierarchy Time Division Multiplexing) connections.